1. Field
This invention relates to processes for removing impurities, especially lead, copper, and iron from molybdenite flotation concentrates.
2. State of the Art
Copper and molybdenum minerals are frequently found together in ore bodies, and are customarily removed from these ore bodies and separated from each other by differential froth flotation. The molybdenite concentrates so obtained contain copper, iron, and lead impurities, which must be removed if the molybdenite is to meet market standards for a high purity product.
Several leach systems have been disclosed in the prior art for removing impurities from molybdenite concentrates. In accordance with U.S. Pat. No. 3,117,860, lead and copper impurities are removed from molybdenum flotation concentrates by roasting the concentrates in the presence of gaseous chlorine at a temperature not above 400.degree. C, preferably between 150.degree. and 300.degree. C, to form soluble chlorides of the copper and lead impurities, which are subsequently leached from the roasted concentrates with water. As demonstrated in Example 4 of that patent, a product containing 0.15% lead could be produced from a feed material containing 0.4% lead; however, to meet market standards for a high purity product, the molybdenite should contain no more than 0.05% lead.
Objectives: The principal objective of this invention was to develop an efficient process capable of removing lead impurities from molybdenum flotation concentrates to produce a product which would meet market requirements for a high purity molybdenite containing no more than 0.05% lead. In addition, a process was sought which would also be effective in removing copper and iron from the molybdenite and which would not result in high molybdenite losses.